1. Field of the Invention
This invention relates to compositions and methods for treating diseases, in particular cancer.
2. Description of the Related Art
Cancer continues to be a major health problem in the United States and the rest of the world. A great deal of money and time is spent each year investigating new therapies and searching for new compounds that have the potential to decrease the mortality associated with cancer. There is also a great deal of effort expended in efforts to decrease the toxicity of existing compounds and therapies.
Neuroblastoma (NB) is the most common extracranial tumor of childhood with approximately 700 new cases per year in the United States. While many infants experience complete regression of primary tumors and even metastatic disease, older children are often confronted with NB metastases that are aggressive and respond poorly to even the most intense multi-component drug regimens. MYCN proto-oncogene amplification occurs in approximately 20% of primary NB tumors, and is strongly associated with advanced stage disease, rapid tumor progression, and poor prognosis (Brodeur G M. (2003) Nat Rev Cancer, 3, 203-16; Brodeur et al., (1984) Science, 224, 1121-4; Seeger et al., (1985). N Engl J Med, 313, 1111-6, each of which is incorporated herein by reference in its entirety).
Polyamine (PA) levels are elevated in many types of cancer, and interference with PA biosynthesis has long been considered a promising therapeutic approach against proliferative diseases, including various malignancies (Schipper et al., (2003) Biochem Soc Trans 31, 375-380; Thomas, T., and Thomas, T. J. (2003) J Cell Mol Med 7, 113-126; Davidson et al., (1999) Endocr Relat Cancer 6, 69-73; Bachrach, U. (2004) Amino Acids 26, 307-309. Epub 2004 June 2022; Milovic, V., and Turchanowa, L. (2003) Biochem Soc Trans 3.1, 381-383; Seiler, N. (2003) Curr Drug Targets 4, 565-585; Seiler, N. (2003) Curr Drug Targets 4, 537-564; Nishioka, K. (1996) Polyamines in cancer: basic mechanisms and clinical approaches; McCann, P. P., and Pegg, A. E. (1992) Pharmacol Ther 54, 195-215; Heby, O., and Persson, L. (1990) Trends Biochem Sci 15, 153-158, each of which is incorporated herein by reference in its entirety). Elevated PA levels have also been detected in urine of cancer patients and can be measured in blood and cerebrospinal fluids (Wallace, H. M., Fraser, A. V., and Hughes, A. (2003) Biochem J 376, 1-14; Bachrach, U. (2004) Amino Acids 26, 307-309. Epub 2004 June 2022, Russell, D. H. (1971) Nat New Biol 233, 144-145, each of which is incorporated herein by reference in its entirety). The naturally occurring PAs are small aliphatic cations. PAs are found in all living cells and are responsible for a plethora of functions including cell growth, differentiation, apoptosis, and DNA replication (Cohen, S. S. (1998) A guide to the polyamines, Oxford University Press, New York; Pegg, A. E. (1986) Biochem J 234, 249-262; Thomas, T., and Thomas, T. J. (2001) Cell Mol Life Sci 58, 244-258, each of which is incorporated herein by reference in its entirety).
Mammalian cells produce the PAs putrescine, spermidine, and spermine (Pegg, A. E. (1986) Biochem J 234, 249-262; Tabor, C. W., and Tabor, H. (1984) Annu Rev Biochem 53, 749-790, each of which is incorporated herein by reference in its entirety). FIG. 1 shows a diagram of the polyamine (PA) biosynthetic pathway and associated amino acids of the urea cycle showing enzymes ODC and AdoMetDC and their specific inhibitors DFMO and SAM486A, respectively. Abbreviations are: AdoMet, S-adenosylmethionine; AdoMetDC, S-adenosylmethionine decarboxylase; AS, argininosuccinate; DFMO, α-difluoromethylornithine (also known as Eflornithine); ODC, ornithine decarboxylase; SAM486A, 4-amidinoindan-1-one 2′-amidinohydrazone (also known as CGP48664A). The diamine putrescine is formed from ornithine via the action of ornithine decarboxylase (ODC), a key enzyme in PA biosynthesis (FIG. 1). Putrescine can be further converted into the higher PAs spermidine and spermine. The aminopropyl groups necessary for these conversions are provided via decarboxylation of S-adenosylmethionine (AdoMet) to decarboxylated S-adenosylmethionine (dcAdoMet) (FIG. 1) (Pegg et al., (1998) Biochem Soc Trans 26, 580-586, which is incorporated herein by reference in its entirety). The positively charged PAs allow for both electrostatic and hydrophobic interactions with DNA, RNA, and proteins, thereby directly affecting gene regulation. There is also increasing evidence that PAs are involved at various stages of signal transduction, and, for example, regulate and phosphorylate important cellular components of the MAPK and PI3K signaling pathways (Chen et al., (2003) Cancer Res 63, 3619-3625; Bachrach, et. al, (2001) News Physiol Sci 16, 106-109; Zhang et. al, (2004) J Biol Chem 279, 22539-22547. Epub 22004 March 22515, each of which is incorporated herein by reference in its entirety).
Normal cell growth and proliferation is orchestrated in a cyclic manner by the action of cyclins and cyclin-dependent kinases (cdks) (Pines, J. (1994) Semin Cancer Biol 5, 305-313, which is incorporated herein by reference in its entirety) and appropriate activation/inactivation of these proteins is necessary for cell cycle progression. The cyclins A, B, D, and E form complexes with corresponding cdks and specifically regulate the G1/S and G2/M phases of the cell cycle. Similarly, ODC and PA concentrations increase in both cell cycle phases (Heby, O. (1981) Differentiation 19, 1-20; Wallace, H. M., Fraser, A. V., and Hughes, A. (2003) Biochem J 376, 1-14, each of which is incorporated herein by reference in its entirety). This strong positive relationship to cell cycle regulation provides further evidence that PAs are intrinsically linked to cell growth and proliferation (Oredsson, S. M. (2003) Biochem Soc Trans 31, 366-370, which is incorporated herein by reference in its entirety).
The proto-oncogene ODC is a key enzyme in polyamine biosynthesis and catalyzes the conversion of ornithine (Orn) to putrescine (Put). The latter is further converted to the higher polyamines spermidine (Spd) and spermine (Spm), all of which have been implicated in tumor cell growth and proliferation. A second rate-limiting enzyme in polyamine biosynthesis is AdoMetDC, which provides the aminopropyl donor decarboxylated S-adenosylmethionine and is required for the sequential conversions of Put to Spd and Spm. Specific inhibitors for both ODC and AdoMetDC are available and have been used in polyamine-related studies.
Alpha-difluoromethylornithine (DFMO, also known as Eflornithine) is a synthetic suicide inhibitor of ODC, which has been evaluated in phase III human clinical trials as an anticancer and chemopreventive agent (Carbone et al., (2001) Cancer Epidemiol Biomarkers Prev, 10, 657-61; Fabian et al., (2002) Clin Cancer Res, 8, 3105-17; Levin et al., (2003) Clin Cancer Res, 9, 981-90; Levin et al., (2000) Clin Cancer Res, 6, 3878-84; Meyskens et al., (1999) Clin Cancer Res, 5, 945-51; Porter et al., (1992) Falk symposium on polyamines in the gastrointestinal tract pp 301-22, each of which is incorporated herein by reference in its entirety). SAM486A (also known as CGP48664), a derivative of the first generation AdoMetDC inhibitor mitoguazone (MGBG), exerts potent and specific inhibition of AdoMetDC (Regenass et al., (1994) Cancer Res, 54, 3210-7; Svensson F, Mett H and Persson L. (1997). Biochem J, 322, 297-302, each of which is incorporated herein by reference in its entirety). Its efficacy has been assessed in various cancer cells and animal systems (Dorhout et al., (1995) Int J Cancer, 62, 738-42; Regenass et al., (1994) Cancer Res, 54, 3210-7; Svensson et al., (1997) Biochem J, 322, 297-302, each of which is incorporated herein by reference in its entirety), and has been evaluated in Phase I and Phase II human clinical trials (Eskens et al., (2000) Clin Cancer Res, 6, 1736-43; Paridaens et al., (2000) Br J Cancer, 83, 594-601; Pless et al., (2004) Clin Cancer Res, 10, 1299-305; Siu et al., (2002) Clin Cancer Res, 8, 2157-66; van Zuylen et al., (2004) Clin Cancer Res, 10, 1949-55, each of which is incorporated herein by reference in its entirety). The high enzymatic activities of ODC and AdoMetDC in rapidly growing cells and tissues, and especially, in tumor cells, rendered a rationale for designing pharmacological inhibitors, which selectively interfere with the natural biosynthesis of PAs and, consequently, prevent tumor cell growth and proliferation.
Although monotherapy with DFMO has been disappointing in most cancer trials, the drug was found more effective as a chemopreventive agent based on its low toxicity. The reported side effects are relatively mild with occasional occurrence of temporary ototoxicity, diarrhea, and some neutropenia. Notably, DFMO is successfully used in the treatment of a number of parasitic diseases, including the infection with Trypanosoma brucei gambiense, which causes African trypanosomiasis (Heby, et al., (2003) Biochem Soc Trans 31, 415-419, which is incorporated herein by reference in its entirety). Recent Phase II clinical trials with SAM486A in patients with relapsed or refractory non-Hodgkin's lymphoma were promising and the most frequent side effects included nausea, vomiting, diarrhea, asthenia, abdominal pain, and flushing (Pless et al., (2004) Clin Cancer Res 10, 1299-1305, which is incorporated herein by reference in its entirety).
It has been found that NB cells respond more rapidly and more profoundly to the growth and proliferation inhibitory effects of DFMO and SAM486A than, for example, ovarian cancer cells or other cell lines discussed in the literature (FIG. 2). Our research further revealed that DFMO and SAM486A are effective against NB cells with MYCN amplification (typically derived from more aggressive NB tumors, which metastasize and do not respond well to conventional chemotherapy) and with mutated tumor suppressor protein p53 (often found in relapsed and chemoresistant NB tumors), thus further supporting the use of these drugs for therapeutic NB treatments.